2.3 Determination of plant growth indicators
One V. natans plant was randomly selected from each column at each sampling time, and after being cleaned, their growth indicators were determined including height, plant biomass, leaf number, and root length. The chlorophyll content and malondialdehyde (MDA) content of leaves were determined by the Lichtenthaler - Arnon method and thiobarbituric acid method, respectively. The superoxide dismutase (SOD) and catalase (CAT) activity were determined by guaiacol method, and root activity was determined by triphenyl tetrazo - lium chloride (TTC) method (Yang et al. 2012).